This study was designed to compare the accuracy of the use of PET/CT and ultrasonography (US) for the detection of recurrence or a metastasis after surgical treatment in patients with differentiated thyroid carcinoma.

A total of 128 patients with differentiated thyroid carcinoma, who had previously undergone a neck operation, were evaluated with the use of PET/CT and US. The two studies were performed within three months of each other. The presence of a metastasis or recurrence was based on histological results. Statistical values for FDG PET/CT and US findings were calculated statistically.

Recurrence or a metastasis occurred in 40 of 128 patients. Thirty-one patients had lesions that were detected with the use of both PET/CT and US. Eight patients had lesions that were detected only with US. A lesion in one patient that had a high SUV on PET/CT was not detected by the use of US. The sensitivity, Specificity, accuracy, positive predictive value and negative predictive value for PET/CT were 80%, 82%, 82%, 68% and 90%, respectively. The corresponding values for US were 97%, 85%, 89%, 75% and 99%, respectively. The sensitivity and specificity for US were higher as compared to PET/CT, with no statistically significant difference.

To detect recurrent or metastatic disease after surgical treatment in patients with differentiated thyroid carcinoma, US of the neck is a better screening modality as compared to the use of PET/CT.